Shape memory polymers are a class of “smart” materials that can memorize and recover their permanent shapes in response to an external stimulus, such as heat, light, solvent, electricity, and magnetic fields.1-15 They have been extensively exploited for a wide spectrum of technological applications, like smart surgical stents and sutures,16-17 implants for minimally invasive surgery,18-19 aerospace morphing structures,20-22 sensors and actuators,23-24 and self-healing materials.25 Compared with their alloy counterparts (e.g., nitinol alloy), SMPs have gained increased attention due to their dramatically larger strain storage and recovery (up to 800% vs. less than 8%), low cost, light weight, ease of synthesis, and biocompatibility.1-2,6-9 Shape memory (SM) is typically achieved in a three-step process that includes programming, storage, and recovery. Programming involves deforming a sample from its permanent shape to a temporary shape. This is usually done above the polymer glass transition temperature (Tg) to take advantage of the compliant nature of SMPs at high temperature. Once the sample has been deformed, it is cooled below Tg to “freeze” in the temporary shape, which is due to restricted polymer chain mobility. Recovery occurs when the sample is heated to the vicinity of Tg, which increases chain mobility and allows the polymer to return to its permanent shape via entropy elasticity.6-9 
The recovery time for thermoresponsive SMPs which are mostly studied and employed in practical devices is usually long—on the order of minutes.7-9 This greatly impedes many applications that require fast response speed. Similar slow response is also suffered by other types of SMPs activated through lasers,26 electricity,27 infrared absorption,28 and alternating magnetic fields.29 Indeed, most of these different SM activation mechanisms are still thermoresponsive as they depend on the generation of heat to trigger the final shape recovery. Additionally, “hot” programming (i.e., heating SMP above a transition temperature such as Tg and then deforming to a temporary configuration) is generally utilized by almost every class of SMPs.1-15 By contrast, SMPs that can be “cold” programmed (i.e., programming at or below ambient temperature), which could provide a wide degree of processability to accommodate broader application requirements (e.g., operating at ambient conditions), are rare.30-31 Moreover, most of current SMP applications focus on leveraging the macroscopic SM effect, where the deformation length-scale is large (on the order of centimeters). Thus, there is a need to overcome these deficiencies.